Growth factors affecting human thrombocytopoiesis: potential agents for the treatment of thrombocytopenia.
Explore the source record for details and available documents.
Animals↗
Biomedical subjects
R Hoffman
Publications and source records attributed to R Hoffman.
Further phenotypic characterization and isolation of human hematopoietic progenitor cells using a monoclonal antibody to the c-kit receptor.
A mouse antihuman monoclonal IgG2a antibody, termed stem cell receptor-1 (SR-1), specific for a determinant of the c-kit ligand receptor (KR), was used as an immunologic probe to analyze KR expression by human bone marrow hematopoietic progenitor cells. Monoclonal antibodies to CD34 and HLA-DR were used in a multicolor staining protocol in conjunction with SR-1 to further define the phenotypes of various classes of hematopoietic progenitor cells. Expression of KR (SR-1+) on hematopoietic progenitor cells identified subpopulations of cells expressing CD34 (CD34+). While one-half of the CD34- and HLA-DR-expressing cells (CD34+ HLA-DR+) expressed the KR (SR-1+), one-third of the CD34+ cells that lacked HLA-DR expression (CD34+ HLA-DR-) were SR-1+. The CD34+ HLA-DR+ SR-1+ cell population contained the vast majority of the more differentiated progenitor cells, including the colony-forming unit (CFU) granulocyte-macrophage; burst-forming unit-erythrocyte; CFU-granulocyte, erythrocyte, macrophage, megakaryocyte; and the CFU-megakaryocyte. The overall progenitor cell cloning efficiency of this subpopulation was greater than 31%. By contrast, the CD34+ HLA-DR- SR-1+ cell population contained fewer of these more differentiated progenitor cells but exclusively contained the more primitive progenitor cells, the BFU-megakaryocyte, high proliferative potential-colony-forming cell, and long-term bone marrow culture-initiating cell. The overall progenitor cell cloning efficiency of this subpopulation was greater than 7%. Both the CD34+ HLA-DR- and CD34+ HLA-DR+ cell subpopulations lacking KR expression contained few assayable hematopoietic progenitor cells. Long-term bone marrow cultures initiated with CD34+ HLA-DR- SR-1+ but not CD34+ HLA-DR- SR-1- cells, which were repeatedly supplemented with c-kit ligand (KL) and interleukin-3, generated assayable progenitor cells of at least 2 lineages for 10 weeks. These experiments demonstrate the expression of the KR throughout the hierarchy of human hematopoietic progenitor cell development. We conclude from our data that the KL and KR play a pivotal role in cytokine regulation of both the primitive and more differentiated human hematopoietic progenitor cells.
Antibodies, Monoclonal↗
Increased circulating nitrogen oxides after human tumor immunotherapy: correlation with toxic hemodynamic changes.
BACKGROUND: Toxicity to interleukin-2 (IL-2) tumor immunotherapy is manifested principally by the vascular leak syndrome, hypotension, and a hyperdynamic response with low systemic vascular resistance. Nitric oxide (.N = O), a recently discovered biological mediator of vascular smooth muscle relaxation, is produced in increased amounts by numerous cell types exposed to a number of inflammatory cytokines. PURPOSE: Our purpose was to determine if there is an increased production of .N = O in patients receiving IL-2 tumor immunotherapy, and, if so, whether increases in .N = O production correlate with hemodynamic instability. METHODS: Twelve patients undergoing immunotherapy trials with IL-2 and anti-CD3 monoclonal antibody-activated lymphocytes (T-AK cells) were studied. Plasma levels of nitrate (NO3-), the stable end metabolic product of .N = O synthesis, were measured before and at the end of IL-2 treatment cycles. RESULTS: We observed a ninefold increase in plasma levels of NO3- in patients after 7 days of treatment (P less than .0001). A significant decrease in both systolic and diastolic blood pressures was observed in all patients (P less than .001). CONCLUSIONS: We propose that mediated induction of .N = O synthase enzyme leads to progressive increases in .N = O production which, in turn, produces clinically significant hypotension. IMPLICATIONS: Since .N = O synthesis can be competitively inhibited by L-arginine analogues, a possible pharmacologic modulation of .N = O production could potentially contribute to better management of toxic side effects seen in IL-2 cancer therapies.
Amino Acid Oxidoreductases↗
Characterization of a scintillation proximity assay to detect modulators of transforming growth factor alpha (TGF alpha) binding.
A scintillation proximity assay (SPA) for transforming growth factor alpha (TGF alpha) using SPA beads coated with A431 membranes has been studied. Binding of TGF alpha to the beads was characteristic of a receptor interaction. A class of high-affinity receptors for [125I]-TGF alpha (Kd = 0.10-0.26 nM) was detected by competition studies between [125I]TGF alpha and cold TGF alpha and by analysis of association and dissociation rate constants. An antibody to the epidermal growth factor receptor (clone 528) inhibited binding of [125I]TGF alpha (IC50 = 0.20 micrograms/ml), but an anti-TGF alpha antibody (clone 134A-2B3) (less than 25 micrograms/ml) did not block binding. Suramin inhibited [125I]-TGF alpha binding (IC50 = 0.20 mM). The ether lipids 1-O-hexadecyl-2-O-methyl-sn-glycero-3-phosphocholine, 1-O-octadecyl-2-O-methyl-sn-glycero-3-phosphocholine, and rac-lyso-platelet activating factor inhibited TGF alpha binding (IC50 values of 49, 69, and 57 microM, respectively). SPA is a convenient method for identifying agents that may act by interfering with TGF alpha binding.
Antibodies, Monoclonal↗
Clinical pharmacokinetic study of tiazofurin administered as a 1-hour infusion.
Tiazofurin, 2-beta-D-ribofuranosylthiazole-4-carboxamide, is cytotoxic to murine and human tumor cells. In earlier Phase-I/-II trials performed in other centers in patients with solid tumors, the drug was given mainly as a 10-min bolus or as a continuous i.v. infusion for 5 days. These protocols were associated with serious side effects, including neurotoxicity, pleuropericarditis, and occasional myelosuppression. In our study, 26 patients with end-stage leukemia were treated with tiazofurin with 1-hr daily i.v. infusions, resulting in lower incidence and less severity of side effects. In this group, 7 attained complete remission and 7 showed hematologic responses. Out of 12 evaluable patients with myeloid blast crisis of chronic granulocytic leukemia, 10 (83%) responded to therapy, with 6 attaining complete response. We present pharmacokinetic parameters of our clinical study and examine some of the reasons for the lower toxicity found in our trials. In leukemic patients during and after infusion at doses of 1,100, 2,200 and 3,300 mg/m2 tiazofurin peak plasma concentrations were 245, 441 and 736 microM, respectively, values one-half of those calculated from other reports with a 10-min bolus administration. In our 1-hr infusion method, biphasic pharmacokinetics were noted with alpha t1/2 and beta t1/2 of 0.5 and 6.2 hr, and tiazofurin was eliminated at a faster rate than in previous trials with continuous infusion. The area under the curve with our 1-hr infusion was 52% of that reported for the same dose given by continuous infusion. Our 1-hr infusion method and prompt and effective treatment of side effects enabled us to administer higher doses and larger total amounts of tiazofurin in longer treatment cycles than in any previous trials elsewhere. Tiazofurin therapy using 1-hr infusion may be feasible for other carefully selected types of malignancies.
Adult↗
Sustained human hematopoiesis in sheep transplanted in utero during early gestation with fractionated adult human bone marrow cells.
Sheep were transplanted in utero during early gestation with subpopulations of adult human bone marrow (BM) cells enriched for human progenitor and hematopoietic stem cells (HSC). Chimerism was documented in three of seven transplanted fetuses using monoclonal antibodies against human-specific hematopoietic cell lineages and/or cytogenetic analysis of BM and peripheral blood cells of recipients. Only chimeric sheep BM cells expressing CD45 (6.0% of total BM cells) formed human hematopoietic colonies in response to human recombinant cytokines as determined by cytogenetic analysis. Sorted CD45+ BM cells developed human T-cell colonies containing CD3+, CD4+, and CD8+ cells. DNA from chimeric BM cells obtained 3 months after birth displayed a finger printing pattern identical to that of DNA from the human donor of the HSC graft. These studies indicate that first trimester sheep fetuses are tolerant of adult human HSC grafts, thus permitting the creation of xenogeneic chimera expressing human myeloid and lymphoid lineages. The present findings also suggest that HSC grafts from immunologically competent, HLA-mismatched adult donors may be useful for correcting human genetic diseases in utero during early gestation.
Animals↗
Relationship between cytokine-dependent cell cycle progression and MHC class II antigen expression by human CD34+ HLA-DR- bone marrow cells.
Human CD34+ HLA-DR- bone marrow cells constitute a phenotypically homogeneous population of quiescent cells. More than 97% of CD34+ HLA-DR- cells reside in the G0/G1 phase of the cell cycle. The in vitro effects of two cytokines, IL-1 alpha and IL-3, alone or in combination, on the viability, cell cycle status and acquisition of HLA-DR by this cell population were examined. Cell viability was preserved in cultures receiving cytokines, but declined steadily in cultures deprived of exogenous IL. Over a period of 4 days, IL-3 progressively induced the expression of HLA-DR although driving corresponding numbers of cells into S and G2 + M. Although IL-1 alpha induced the expression of HLA-DR, it was not as effective as IL-3 in promoting the exit of these cells from G0/G1. Combinations of IL-1 alpha and IL-3, however, exerted an even greater effect on promoting both HLA-DR expression and entry of cells into active phases of the cell cycle. Simultaneous measurement of HLA-DR expression and cell cycle status in response to IL-1 alpha and IL-3 indicated that the majority of de novo expression of HLA-DR occurred in cells that remained in G0/G1. CD34+ HLA-DR- cells cultured with IL-1 alpha and IL-3 but arrested in G0/G1 by hydroxyurea were still capable of expressing HLA-DR, demonstrating that the acquisition of HLA-DR was independent of the entry of these cells into active phases of the cell cycle. These data indicate that the survival, HLA-DR expression, and cell cycle status of human CD34+ HLA-DR- bone marrow cells are governed by regulatory cytokines such as IL-1 alpha and IL-3. In addition, the entry of these cells into active phases of the cell cycle does not seem to be a prerequisite for the expression of HLA-DR, nor does it seem that the acquisition of HLA-DR by hematopoietic progenitor cells is a marker of cells entering the S phase of the cell cycle.
Antigens, CD↗
Role of c-kit ligand in the expansion of human hematopoietic progenitor cells.
To test the hypothesis that the c-kit ligand plays an important role in the regulation of early events occurring during human hematopoiesis, we determined the effect of a recombinant form of c-kit ligand, termed mast cell growth factor (MGF), on the high-proliferative potential colony-forming cell (HPP-CFC) and the cell responsible for initiating long-term hematopoiesis in vitro (LTBMIC). MGF alone did not promote HPP-CFC colony formation by CD34+ DR- CD15- marrow cells, but synergistically augmented the ability of a combination of granulocyte-monocyte colony-stimulating factor (GM-CSF) interleukin (IL)-3 and a recombinant GM-CSF/IL-3 fusion protein (FP) to promote the formation of HPP-CFC-derived colonies. MGF had a similarly profound effect on in vitro long-term hematopoiesis. Repeated additions of IL-3, GM-CSF, or FP alone to CD34+ DR- CD15- marrow cells in a stromal cell-free culture system increased cell numbers 10(3)-fold by day 56 of long-term bone marrow culture (LTBMC), while combinations of MGF with IL-3 or FP yielded 10(4)- and 10(5)-fold expansion of cell numbers. Expansion of the number of assayable colony-forming unit-granulocyte-monocyte (CFU-GM) generated during LTBMC was also markedly enhanced when MGF was added in combination with IL-3 or FP. In addition, MGF, IL-3, and FP individually led to a twofold to threefold increase in HPP-CFC numbers after 14 to 21 days of LTBMC. Furthermore, the effects of these cytokines on HPP-CFC expansion during LTBMC were additive. Throughout the LTBMC, cells receiving MGF possessed a higher cloning efficiency than those receiving IL-3, GM-CSF, or FP alone. These data indicate that the c-kit ligand synergistically interacts with a number of cytokines to directly augment the proliferative capacity of primitive human hematopoietic progenitor cells.
Antigens, CD↗
Role of cytokines in sustaining long-term human megakaryocytopoiesis in vitro.
An in vitro liquid suspension culture system was used to determine the role of cytokines in sustaining long-term human megakaryocytopoiesis. Bone marrow cells expressing CD34 but not HLA-DR (CD34+DR-) were used as the inoculum of cells to initiate long-term bone marrow cultures (LTBMC). CD34+DR- cells (5 x 10(3)/mL) initially contained 0.0 +/- 0.0 assayable colony-forming unit-megakaryocytes (CFU-MK), 6.2 +/- 0.4 assayable burst-forming unit-megakaryocytes (BFU-MK), and 0.0 +/- 0.0 megakaryocytes (MK). LTBMCs were recharged every 48 hours with granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-1 alpha (IL-1 alpha), IL-3, and/or IL-6, alone or in combination. LTBMCs were demidepopulated weekly or biweekly, the number of cells and MK enumerated, and then assayed for CFU-MK and BFU-MK. LTBMCs receiving no cytokine(s) contained no assayable CFU-MK or BFU-MK and no observable MK. LTBMCs receiving GM-CSF, IL-1 alpha, and/or IL-3 contained assayable CFU-MK and MK but no BFU-MK for 10 weeks of culture. The effects of GM-CSF and IL-3, IL-1 alpha and IL-3, but not GM-CSF and IL-1 alpha were additive with regards to their ability to augment the numbers of assayable CFU-MK during LTBMC. LTBMCs supplemented with IL-6 contained modest numbers of assayable CFU-MK for only 4 weeks; this effect was not additive to that of GM-CSF, IL-1 alpha, or IL-3. The addition of GM-CSF, IL-1 alpha, and IL-3 alone or in combination each led to the appearance of significant numbers of MKs during LTBMC. By contrast, IL-6 supplemented cultures contained relatively few MK. These studies suggest that CD34+DR- cells are capable of initiating long-term megakaryocytopoiesis in vitro and that a hierarchy of cytokines exists capable of sustaining this process.
Antigens, CD↗
Relapsing polychondritis: a paraneoplastic syndrome associated with myelodysplastic syndromes.
We report an unusual case of a patient with a myelodysplastic syndrome associated with life threatening relapsing polychondritis. The improvement in symptoms attributable to the relapsing polychondritis during treatment of the hematologic disorder suggests that relapsing polychondritis is a paraneoplastic syndrome associated with myelodysplastic syndromes.
Adult↗
Hypolipidemic drugs reduce lipoprotein susceptibility to undergo lipid peroxidation: in vitro and ex vivo studies.
Oxidized LDL, which has been discovered in vivo in areas of proximity to the atherosclerotic lesion, has been shown to enhance macrophage cholesterol accumulation. We studied the anti-oxidant potential of pravastatin, bezafibrate and cholestyramine in 18 patients with hypercholesterolemia. In addition, we examined the electrophoretic mobility and the uptake of LDL by macrophages before and after drug therapy. Pravastatin lowered plasma levels of LDL cholesterol by 57%, cholestyramine by 27% and bezafibrate by 25%. Pravastatin and bezafibrate also altered the composition of LDL as evidenced by the reduction of its cholesterol/apo B100 ratio. Pravastatin and bezafibrate reduced plasma triglyceride levels by 45% and 25%, respectively, whereas cholestyramine raised plasma triglyceride concentrations by 28%. LDL propensity for in vitro oxidation was analyzed following lipoprotein incubation with 10 microM copper ions and determination of LDL malondialdehyde (MDA), peroxides (PD) and conjugated dienes (CD) content. All drugs inhibited the susceptibility to in vitro oxidation of LDL isolated after drug therapy in comparison to LDL isolated before commencing drug therapy. Pravastatin reduced MDA content by 22%, PD by 18% and CD by 20%. Cholestyramine reduced LDL content of MDA by 41%, PD by 25% and CD by 63%. Bezafibrate reduced MDA by 41%, PD by 38% and CD by 45%. LDL vitamin E content was reduced after treatment with bezafibrate, pravastatin and cholestyramine by 49%, 36% and 8%, respectively. The electrophoretic mobility of LDL after all drug therapies was reduced in comparison to LDL obtained before therapy. Macrophage uptake of LDL assessed by either the cellular cholesterol esterification rate or by lipoprotein degradation was not affected by drug therapy.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Phase I trial of temozolomide (CCRG 81045: M&B 39831: NSC 362856).
Temozolomide (CCRG 81045: M&B 39831: NSC 362856) is an analogue of mitozolomide displaying similar broad spectrum activity in mouse tumours, but showing considerably less myelosuppression in the toxicology screen. Temozolomide was initially studied intravenously at doses between 50-200 mg m-2 and subsequently was given orally up to 1,200 mg m-2. A total of 51 patients were entered on the single dose schedule. Temozolomide exhibits linear pharmacokinetics with increasing dose. Myelotoxicity was dose limiting. Experimentally, temozolomide activity was schedule dependent and therefore oral administration was studied as a daily x 5 schedule between total doses of 750 and 1,200 mg m-2 in 42 patients. Myelosuppression was again dose limiting. The recommended dose for Phase II trials is 150 mg m-2 po for 5 days (total dose 750 mg m-2) for the first course, and if no major myelosuppression is detected on day 22 of the 4 week cycle, the subsequent courses can be given at 200 mg m-2 for 5 days (total dose 1 g m-2) on a 4 week cycle. Mild to moderate nausea and vomiting was dose related but readily controlled with antiemetics. Clinical activity was detected using the 5 day schedule in four (2CR, 2PR; 17%) out of 23 patients with melanoma and in one patient with mycosis fungoides (CR lasting 7 months). Two patients with recurrent high grade gliomas have also had partial responses. Temozolomide is easy to use clinically and generally well tolerated. In the extended Phase I trial temozolomide only occasionally exhibited the unpredictable myelosuppression seen with mitozolomide.
Adult↗
Retroviral-mediated gene transfer of bone marrow cells during autologous bone marrow transplantation for acute leukemia.
Explore the source record for details and available documents.
Bone Marrow Transplantation↗
Animal models for human hematopoiesis.
Despite seminal contributions provided by in vitro studies to the field of hematopoiesis, our present knowledge of mammalian lymphohemopoiesis and the mechanisms governing differentiation and self-renewal of hematopoietic stem cells has been derived in most part from elegant in vivo studies. The inability to apply such an approach to the examination of the human hematopoietic system is the primary reason why several aspects of human hematopoiesis including human stem cell biology are still poorly understood. To overcome the inability to probe human hematopoiesis in vivo, researchers have "humanized" animals via the transplantation of human hematopoietic progenitor cells and other tissues in an attempt to create human-animal chimera suitable for investigating human lymphohematopoiesis in vivo. To date, several of these "humanized" animal models have been developed. During their relatively short existence, human-animal models have contributed substantially to the field of experimental hematology. The development, peculiarities, shortcomings, and applications of these animal models as well as their potential use in exploring the field of human lymphohematopoiesis are the focus of this review.
Animals↗
Left posterior hemiblock related to an interventricular septum tumour. First case in the literature.
A 22-year-old man who engaged in intense and regular physical exercise complained of atypical chest pain. The only remarkable abnormality found in the routine clinical work-up was a left posterior hemiblock. The echocardiogram and the magnetic resonance imaging (MRI) study showed a tumour in the posterior and superior aspect of the interventricular septum where the posterior fascicle of the left bundle is located. It was interpreted that the left posterior hemiblock was produced by the tumour.
Adult↗
Human hematopoietic stem cell adherence to cytokines and matrix molecules.
The hematopoietic microenvironment is a complex structure in which stem cells, progenitor cells, stromal cells, growth factors, and extracellular matrix (ECM) molecules each interact to direct the coordinate regulation of blood cell development. While much is known concerning the individual components of this microenvironment, little is understood of the interactions among these various components or, in particular, the nature of those interactions responsible for the regional localization of specific developmental signals. We hypothesized that cytokines act together with ECM molecules to anchor stem cells within the microenvironment, thus modulating their function. In order to analyze matrix-cytokine-stem cell interactions, we developed an ECM model system in which purified stem cell populations and plastic-immobilized individual proteins are used to assess the role of various matrix molecules and/or cytokines in human hematopoietic cell development. Analysis of these interactions revealed that a single ECM protein, thrombospondin, in conjunction with a single cytokine (e.g., c-kit ligand), constitutes a developmental signal that synergistically modulates hematopoietic stem cell function.
Antigens, CD↗
Selection of BCR/ABL-negative progenitor cells from chronic myeloid leukemia marrow.
Explore the source record for details and available documents.
Antigens, CD↗
Effects of adherent bone marrow stromal cells on the development and proliferation of highly purified human hematopoietic stem cells.
Explore the source record for details and available documents.
Bone Marrow Cells↗